Propellent powders



Patented Sept. 6, 1949 PROPELLENT POWDERS' George C. Hale and Ludwig F. Audrieth, Dover, N. J.

No'rDi'awing Application March 10, 1947; l Serial No. 733,717.

.(Grantedlunder the act of March 3', 1883, as"

5 Claims.

The-invention described herein may be manufactured-and used byor for the Government for governmental purposes without: the payment to us ofiany: royalty thereon.

This invention relates to. propellent powders containing-T new and novelconstituents chosen from among, thec-lassof materials known as the tetrazoles.

The tetrazoles are characterized by the type formula where X representshydrogen or some negative group such asihydroxyl, amino, halogenor a low molecular weight alkyl radical and. where R represents hydrogen or some low molecular weight alkyl-radicaL- While. these materials as a class are indicated to impa-rt desirable characteristics to propellent powders containing them, we emphasize particularly 5-aminotetrazole as an outstanding example of this/class of compounds in view of the fact that it imparts veryunusual and. highly favorable properties to powders which contain this agent.

Inthe design and manufacture of modern propellants; in; particular for military purposes, everyi eiiort' is-made to achieve bothsmokelessness and flashlessness. An effort-is made to approach these 'idealzreqwsites for the reason that gun" positions are revealed by day if the gases resulting from the burning of the propellent powder containz appreciable. quantities of solid particle in suspension, thereby producing smoke and are rovealedby night if these same gases undergo vigorous combustion "on issuing from the muzzle of thegun; producing what isk'commonly knownas muzzle flash. Smokelessness has been achieved by several means:

a. By the use of'nitroce llulose with a relatively high nitrogen content;

b. By the use of'addends' which either materially increase the oxygen balance of the propellent powder: or-give what is known as a hotter propellant thus insuring complete combustion.

o. By modifying: the ignition'systemin. order to effect morecompletecombustion-as well as ,more rapid :cor-nbustiom combustion:

amended-April 30, 1928; 3'70" 0.- G; 757) as to prevent subsequent burning on contactwith the atmosphere. The facttliatthe temperature of these gases is above that ofthe explosion temperature for some of the combustible constituents, such as carbon monoxide and methane, invariably produces a large and prominent'flash. Since these smokeless propellants have-a high energy content, and develop high temperatures on reaction, excessive erosionof thegun barrel is thereby effected with the result" that the life of the weapon is considerably reduced.

Flashlessness is generallyattained by the addition of some inert constituent; either organic or inorganic such as dibutylphthalate, triacetin, potassium sulfate and other alkali sulfates, or potassium bi-tartrate. While the mechanism of their eiiect in reducing flash is not fully understood; flash is to a large degree eliminated, but

in so doing considerable smoke is formed; Since these fias'li-reducing agents are inert; provision must be made in the design of the powder, in

its composition and in the'quantity'used'for the reduction in potential occasioned thereby. Flash charges in'the cartridgecase or may be incorporated directly into the powder.

Efforts have also been made to devise flashless powder compositions by" the use of cool explosives such as nitroguanidine. Nit'roguanidine has a very low explosion temperature and may replace nitrocellulose in propellent powders without afiecting too gr'eatly the ballistic potential of the powder. The nitroguanidine powders are, however, objectionable because'of the fact that considerable: quantities of toxic gases such' as ammonia are found to be among the'products of I Even though flashlessness is achieved; such nitroguanidine powders are not suffi'ciently smokelessto be acceptable'for various weapons;

It would appear from these recitations of prior art: that the two objectives, 1: e1, smokelessness and flashlessness: have not yet been. attained i in any one powder: to' the: extent desired by any present procedure involving either design. or change in composition; ofi'the J powder. A flashless powder achieves this 'requirementiat the expense" of considerable smoke, whereas a smoke less' powder is invariably characterized by' the development of 1 a 1 considerableamount of muzzle flash.

We have found that the tetrazoles as a class do in fact achieve these two objectives to a degree heretofore unattained in propellent powders.

The tetrazoles are compounds containing a high nitrogen content. Aminotetrazole in particular has a nitrogen content of 82.3%. When incorporated in a propellent powder with a nitrocellulose base it undergoes burning and decomposition with the formation of a large volume of nitrogen gas, thus diluting the combustible products remaining in the propellent gases. Unlike other addends, this decomposition or burnin of aminotetrazole is not accompanied by any marked reduction in ballistic potential. By proper formulation of powders using the tetrazole, flash may be considerably reduced or entirely eliminated in various weapons. Aminotetrazole is unique among flash reducing agents in that it does not produce a large amount of smoke. Laboratory as well as surveillance tests of aminotetrazole powders indicate that these are more stable than many double base powders. Powders manufactured containing aminotetrazole have been found to be of acceptable mechanical strength and to give in closed bomb firings, relative force and relative quickness characteristics comparable to those of standard powders now in use. Actual gun firings furthermore demonstrate that the pressures developed as well as the projectile Velocities achieved compare favorably with standard powders now in use. Our experimental work, therefore demonstrates that these aminotetrazole powders possess the necessary requisites of standard powders and in addition impart those very desirable characteristics of flashlessness and smokelessness to the propellant.

We have found that the mechanical addition zole together with nitrocellulose (13.15% nitrogen content) and diphenyl amine as a stabilizer. Such powders have thermochemical properties as determined by heat of explosion and gas volume measurements which are closely akin to the nitrocellulose powders in use for this weapon. Such powders give little or no flash and in addition give only a slight amount of smoke. Other powders have been made for other weapons with equally desirable characteristics. The replacement of some of the nitrocellulose by nitroglycerin or dinitro ethyl benzene or mixtures of the nitro ethyl benzenes as covered in U. S. Patent 1,963,992 gives increased plasticity to such aminotetrazole powders and at the same time renders them resistant to absorption of moisture. It should be emphasized again that incorporation of aminotetrazole does not reduce the ballistic potential of the powder as much as when an inert flash reducing agent is employed.

There follows specific compositions of powder which in proper granulation gave acceptable ballistic results when fired in the caliber .50 rifle and 3 A. A. gun respectively. Flashlessness was obtained with markedly improved smoke efiects when compared with standard powders.

3" A. A. gun, M42 projectile.

This invention, therefore covers propellent powders for use in small arms or cannon, such powders containing aminotetrazole, to provide fiashlessness without excessive smoke. The efiect of such addition does not decrease the stability of the powders, does not reduce the ballistic potential of such compositions unduly and is unique in ofi ering for use fiashless powders which yield a greatly reduced amount of smoke.

We claim:

1. A propellent powder comprising nitrocellulose as the main explosive ingredient and a smaller proportion of fi-aminotetrazole in sufiicient amount to impart flashless and smokeless characteristics to the powder. 2. A propellent powder comprising nitrocellulose as the main explosive ingredient and about 20 to 25% of 5-aminotetrazole based upon the weight of the powder.

3. A propellent charge comprising nitrocellu- 40 lose as the main explosive ingredient and a suflicient amount of 5-aminotetrazole to impart flashless and smokeless characteristics to the charge.

4. A propellent charge comprising nitrocellulose as the main explosive ingredient and about 20% of S-aminotetrazole based upon the weight of the charge.

5. A propellent charge comprising nitrocellulose as the main explosive ingredient and about 0 20 to 25% 5-aminotetrazole based upon the weight of the charge.

GEORGE C. HALE. LUDWIG F. AUDRIETI-I.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 0 Number Name Date 1,580,572 Rathsburg Apr. 13, 1926 2,066,954 Von Herz Jan. 5, 1937 2,379,056 Alexander June 26, 1943 OTHER REFERENCES The Chemistry of Powder and Explosive, by Davis; John Wiley 8: Co., 1110., N. Y., 1943, vol. II, page 447. (Copy in Division 43.)

Richters Organic Chemistry, vol. 111, pages 144-146, pub. by P. Blakestons Son 8; Co., Phila., 1923. (Copy in Division 43.) 

